a(n) = (3n)!/(n!(n+1)!(n+2)!).
A161581
a(n) = (3n)!/(n!(n+1)!(n+2)!).
Terms
- a(0) =21a(1) =231a(2) =3003a(3) =43758a(4) =692835a(5) =11685817a(6) =207157665a(7) =3823000545a(8) =72931087320
External references
- oeis: A161581
A161581
a(n) = (3n)!/(n!(n+1)!(n+2)!).